Catadioptric objective comprising two intermediate images

ABSTRACT

An objective comprising axial symmetry, at least one curved mirror and at least one lens and two intermediate images. The objective includes two refractive partial objectives and one catadioptric partial objective. The objective includes a first partial objective, a first intermediate a image, a second partial objective, a second intermediate image, and a third partial objective. At least one of the partial objectives is purely refractive. One of the partial objectives is purely refractive and one is purely catoptric.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention is related to a catadioptric objective comprising twointermediate images.

TECHNICAL FIELD

Such is known from U.S. Pat. No. 4,701,035 to Hirose as amicrolithographic projection exposure system. The objective shown therein FIG. 12 comprises two catoptric partial objectives and onecatadioptric partial objective. All objectives are off-axis, not axiallysymmetric, purely spherical systems.

Catadioptric objectives with one intermediate image and a refractivepartial objective are known as microlithographic projection systems withaxial symmetry and central obscuration from U.S. Pat. No. 5,488,299 toElliott and Shafer and from DE 196 39 586 (U.S. Ser. No. 09/263,788 ) toSchuster, the latter being assigned to the assignee of this invention,and incorporated herein by reference.

Elliott and Shafer show the intermediate image near to the centralopening of one of the mirrors, and lenses are arranged in the light pathbetween the mirrors forming Mangin mirrors. All their optical surfacesare spherical.

Schuster shows only the mirrors to be aspherical and avoids big lensesin the beam path between them.

U.S. Pat. No. 5,004,331 to Haseltine et al. discloses a catadioptricprojector for projecting an image to a dome (of a flight simulator). Thesystem comprises an external entrance pupil as means for receivingsubstantially collimated light, a refractive subsystem of rotationallysymmetric, coaxial lenses forming a pupil image which is situated at thecentral opening of an aspheric concave mirror, which together withanother concave mirror forms a reflective pupil relay system. Bothmirrors are tilted with respect to the optical axis of the refractivesubsystem. The whole system provides a wide field of view image on aspherical dome. Full visible spectrum colour correction is obtained bycombination of different glass.

SUMMARY OF THE INVENTION

It is an object of the invention to provide new design alternativeswhich allow for high resolution objectives with reduced lens diametersand high performance. Advantageously these designs are to be used in theVUV spectral region for microscopy or microlithography.

The solution of this problem is obtained by an objective comprisingaxial symmetry, at least one curved mirror and at least one lens and twointermediate images. The objective includes two refractive partialobjectives and one catadioptric partial objective. The objectiveincludes a first partial objective, a first intermediate image, a secondpartial objective, a second intermediate image, and a third partialobjective. At least one of said partial objectives is purely refractive.One of the partial objectives is purely refractive and one is purelycatoptric.

Axial symmetry together with two intermediate images, two refractive andone catadioptric partial objectives, two intermediate images and atleast one refractive partial objective are varied descriptions of thenovel aspects of the invention.

Another aspect that clearly groups the mirrors in one catoptric partialobjective, which cooperates with one or more purely refractive partialobjectives. In this case it is provided that the catoptric partialobjective carries the burden of Petzval sum reduction or fieldflattening. This relieves the refractive partial objective from the needfor beam contractions and expansions by negative and positive lensgroups, as is long established with microlithographic projectionexposure lenses, see e. g. Glatzel E., ZEISS-Information 26 (1981), p.8-13, U.S. Pat. No. 5,260,832 or U.S. Pat. No. 5,903,400. In consequencethe refractive partial objective is simplified and the lens diametersare reduced. Especially for the proposed use in the VUV spectral regionthis gives great relief to the materials supply of suitable crystals orquartz glasses.

The preferred embodiments also are related to the cited Schuster orElliott and Shafer designs with two coaxial central obscuration opposingconvex mirrors, which allows for a very convenient axial asymmetricconstruction of the objective. Such inter alia has advantages inmechanical rigidity and in compatibility with establishedstepper/scanner architectures adapted to refractive objectives.

As a central obscuration in principle has degenerating effects inimaging—though in many cases decidedly taken advantage of as in annularor quadrupole illumination or in pupil filtering and apodisation—thereduction of the obscuration by the central hole of the mirrors of thisdesign is of importance.

A preferred way of reducing obscuration is achieved by placing theintermediate images in the vicinity of the mirrors.

In an alternative embodiment, lenses are inserted between the mirrors.As negative lenses these cooperate with the mirrors to give singlematerial colour correction, relieving the need for band narrowing thelaser light source or for using an achromatizing material pair in theVUV.

The chief ray height at each of the mirror bores is approximately thesame in value, but opposite in sign. This measure allows for minimalcentral obscuration.

The sequence where the mirror-containing partial objective is framed bythe two refractive partial objectives is preferred as it allows for bothintermediate image “planes” connected by the mirror containing partialobjective to be curved such as to best exploit the specific correctioncapabilities of this partial objective.

While it is rather conventional that mirrors are aspheric also in therelated art, in the present invention it is specifically stated thataspheric lens surfaces prove advantageous with this design. Alladvantages and restrictions as recently established for refractiveprojection exposure objectives, see e. g. patent application DE 199 22209 of Schuster (corresponds to U.S. patent application Ser. No.09/760,066, filed Jan. 12, 2001, now U.S. Publication No. 2002/0149855,published Oct. 17, 2002 ) and references cited therein, as incorporatedherein by reference, hold also for the use of aspheric surfaces in thedesigns of this invention.

Diffractive surfaces, as occasionally also proposed for projectionexposure objectives, are also useful with this invention just as theyare with refractive designs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail based on the examples shown inthe drawings.

FIG. 1 shows the lens section of an example of an objective with arefractive, a catadioptric, a second refractive partial objective insequence, reduction ratio 1:6.

FIG. 2 shows another example of such an objective with reduction ratio1:5.

FIG. 3 shows a schematic lens arrangement of an objective with a purelycatoptric partial objective of axial symmetry.

FIG. 4 shows another example of the invention with a refractive, acatoptric, a second refractive partial objective in sequence.

FIG. 5 shows schematically a microscope with an objective according tothe invention.

DETAILED DESCRIPTION OF THE INVENTION

The example of FIG. 1 is a 6:1 reduction objective for a scannerprojection exposure apparatus of microlithography, with an image fielddiameter of 18.4 mm, an image side NA=0.75, being telecentric in theobject space and the image space.

All lenses are made of fluorite CaF₂ and the system is adapted forillumination by the F₂ excimer-laser at 157 mm.

Certainly modifications for other wavelengths with other materials arepossible, e. g. 193 nm and quartz glass.

The first partial objective S1 is refractive and has a reduction ratioof−1/4,27.

It shows two distinct lens groups LG1 of four relatively big lenses ofabout 130 mm diameter, and after the aperture plane a second lens groupLG2 with significantly reduced diameter of about 80 mm and less. Here,the only aspheric lens surface is provided on surface 9 immediatelysubsequent to the aperture plane. Subsequent to the first intermediateimage IMI 1, the second partial objective S2 is catadioptric with twoopposite concave aspheric mirrors M1, M2 with central holes and twonegative meniscus lenses 25, 26 and 27, 28 arranged between them. Theyare passed by the light beams three times. Its magnification ratio is−1/0,99.

Such a magnification ratio near unity allows for a highly symmetricconstruction and optimal correction of distortions.

This arrangement is particularly suitable for chromatic correction andcorrection of field curvature, too. Therefore even with only one lensmaterial CaF₂ a relatively wide laser bandwidth of +−1.2 pm of anunnarrowed F2-laser is accepted by this objective.

Subsequent to the second intermediate image IM12 the third partialobjective S3 again is refractive.

It takes up the divergent light beam with a strongly bent meniscus29,30. A positive air lens—i. e. an air space in the form of a positivelens—between the lens surfaces 40 and 41 is characteristic.

With its reduction ratio of −1/1,42 the overall reduction ratio of thesystem is reached.

The detailed data of Table 1 show that the objective is composed ofrelatively few elements of limited diameters which helps for practicalfeasibility, as CaF₂ is very expensive and of limited availability. Alsothe light path in CaF2 is limited, thus reducing the problem ofsignificant absorption at 157 mm.

The central obscuration necessitated by the fully coaxial constructionof the catadioptric second partial objective S2 is a certain drawback,as such in principle deteriorates the modulation transfer function of anobjective.

However, even in common refractive projection exposure objectives asmall but distinct central obscuration is entered to accommodate beampaths of alignment systems etc.

Efforts are taken in the design to keep the central obscuration small,even with mirror diameters of practical size.

It was found that the diameter of the holes in the mirrors is minimizedwhen the chief ray height is of equal value at the two holes, butopposite in sign.

Further the mirror holes are arranged next to the two intermediateimages IMI 1 and IMI 2, where the beam diameters are at a minimum. Alsothe first partial objective S1 has substantial image reduction to keepthis hole absolutely small, so that also the total mirror diameter islimited to a practical compact value.

The mirror holes are sized to be 2,0 mm larger in diameter than theclosest ray at the edge of the field.

It is recommended that a obscuration mask is inserted at the pupil(aperture) plane of the second partial objective S2—just in front oflens surface 9. This should be sized 20,25% in diameter—equal to 4,1% inarea. Then the area obscuration at the edge of the field has the samevalue as at the center and the MTF curves are completely uniform overthe field.

The wavefront correction of this example is better than 0,011 waves rmsover the field of 17×7 mm² and less than 0,009 waves rms over the fieldof 17×6 mm². The distortion is 2.4 ppm and the median shift is 10 nm.

Colour correction reaches CHL=34 nm/pm for longitudinal colour, so thata+−1.2 pm bandwidth of an unnarrowed F2-laser can be accepted.

The example of FIG. 2 and table 2 has an increased image field of 22×9mm² as well as a significantly increased NA=0,75, while the reductionratio is changed to 5:1. The system is of overall similarity with thefirst example, but with some significant deviations.

The first refractive partial objective S1 has its aperture planeenclosed by two menisci 209, 210 and 211, 212 which are concave towardsthe aperture plane. Here, an obscuring disk OD is inserted for thepurpose of field-independent obscuration as described above.

Two lens surfaces 209 and 217 are aspheric, the first is next to theaperture plane to affect angle deviations and the second is more in thefield region.

The imaging ratio of the first partial objective S1 is −1/4,67.Therefore the catadioptric partial objective can be so small.

The second partial objective S2 again is catadioptric with two asphericmirrors M21, M22 and two negative meniscus lenses 223,224 and 225,226.Now their distance has strongly decreased, but angles increased in thebeam path. This allows for very limited diameters of only 230 mm at thegiven large field and large NA. The reduction ratio is −1//0,97. In thisembodiment, too, the central obscuration is 20% in diameter constantover the full field.

High NA of 0,7 at the intermediate images to allow for the small holesin the mirrors M21, M22 and a rather strong refractive power of thelenses 223,224 and 225,226 in between to give the required colourcorrection are specific to this example.

The mirrors M21, M22 are aspheric with maximum deviations from spherebeing limited to 150 micrometers, which allows for good production andtesting.

Also on the lenses between the mirrors aspheric surfaces could increaseimage quality. A third negative lens here would further optimize colourcorrection, if needed.

The third partial objective S3 shows the characteristic first meniscuslens 227,228 to be even more bent than in FIG. 1. This helps for comacorrection. Also the second lens 229, 230 is a meniscus concave on theintermediate image IMI side, as the two final lenses 249,250 and 251,252are menisci concave towards the image plane Im, what is preferred foraplanatism and correction of spherical aberration.

The positive air lens arranged between the lens surfaces 238 and 239corrects the main part of spherical aberration. For this effect it ispreferably arranged more in the pupil region of the objective than in afield region. However its arrangement before the pupil plane enables itto affect also the oblique spherical aberration in tangential andsagittal direction.

As a meniscus concave toward the pupil plane, lens 245,246 together withthe air space created in front of it assists to the effects of theaforementioned air space.

The imaging ratio of this third partial objective S23 is −1/1,11 nearunity. However, the arrangement is far from symmetry to the pupil plane,so that the strongly distorted intermediate image IMI can be transformedto a highly corrected image at the image plane Im.

Each partial objective has its part of the burden: S21 performs thereduction, S22 makes the colour and Petzval correction and S23 makes thefine tuning of imaging errors.

This second embodiment is not finely tuned to best error correction, butgives the principles of feasibility of such a design.

The aspheric surfaces of both examples of tables 1 and 2 are describedbyz=AS2×h⁴+AS3×h⁶+AS4×h⁸+AS5×h ¹⁰+AS6×h¹²=AS7×h¹⁰with z=axial deviation from sphere, h=radial height from optical axis.

The example of FIG. 3 has a purely catoptric partial objective S31 and apurely refractive partial objective S32 between object Ob and image Im,with intermediate image IMI. This avoids the big negative lenses f thecatadioptric partial objectives of the aforementioned examples. Themirrors M1, M2 now are purely used for Petzval correction—correction offield curvature.

The chromatic characteristics of the objective are defined by therefractive partial objective S32. Use of different lens materials allowsfor achromatization. For DUV/VUV excimer laser systems combinations offluorides, namely calcium fluoride (fluorspar, fluorite), bariumfluoride, strontium fluoride, NaF, Lif etc. and/or quartz glass, also inspecifically doped versions, are adequate. Thus, for microlithography at157 nm, positive lenses L1,L3 can be made of calcium fluoride andnegative lens L2 can be made of barium fluoride or NaF, for example.

Naturally the refractive partial objective S32 has more lenses in arealistic microlithography or microscope objective and the lenses L1 toL3 shown are only schematic representatives.

As the refractive partial objective S32 of this catadioptric objectiveas compared to a full refractive system is relieved from the burden ofPetzval correction, it can be simplified. The waist and bulgeconfiguration with two and more waists of state-of-the-art refractivemicrolithographic reduction projection objectives is therefore notneeded. Only one waist of minor beam reduction remains. Consequently therefractive partial objective S32 can be shorter, smaller in diameter andcan have less lenses. Transmission and contrast are thus increased,while cost is decreased. Aspheric lens surfaces further help in thiseffect.

As the catoptric partial objective S31 is free of lenses, its diameteris not critical: Precision aspherical mirrors with diameters of morethan one meter are state of the art in astronomy, for example.

Obviously the arrangement of catoptric and refractive partial objectivealso can be changed in sequence. Then the diameter of the catoptricpartial system is reduced in consequence of the imaging ratio of therefractive partial objective.

For reasons of good accessibility of object Ob and image Im and of moredesign space for correction, it is advantageous if this system also isextended to a first refractive partial objective S41, a catoptricpartial objective S42 and a second refractive partial objective S43 withintermediate images IMI1 and IMI2, as shown in the example of FIG. 4.

The advantages of the first two embodiments with minimal obscuration andof the third example without big lenses between the mirrors M1, M2 canthus be combined.

Table 3 gives the design data of this example. This is a 157 nmobjective with all crystal lenses, most of LiF and some of NaF, givingexcellent chromatic properties for an unnarrowed F₂ laser with 1,5 pmband width. Reduction ratio is 1:5, maximum image field height is 11,88mm, NA=0,75. Maximum lens diameter is 190,5 mm, maximum mirror diameteris 201 mm. The overall length Ob-Im is 1,459 m.

The use of crystal lenses in DUV to VUV microlithographic objectives ismade here in adaptation of the earlier application DE 199 29 701.0 datedJun. 29, 1999 (99032 P) (corresponding to U.S. Pat. No. 6,683,729 issuedJan. 27, 2004 ) of co-inventor Schuster and the same assignee. Thiscited application as a whole shall be part of the disclosure of thisapplication, too.

Consequently, negative NaF lenses are entered, plus one positive NaFmeniscus 408, 409 in the first partial objective S41, which reduceslateral chromatic aberration, in an overall LiF lens system.

Aspheric surfaces are entered into this design at a number of surfaces,where this is advantageous. Consequently, also the mirrors 440 and 441are aspheric.

In the first, reducing partial objective S41, the second bulge comprisesone asphere, the second waist one asphere, and the third bulge 2aspheres. In the third partial objective S43 the first bulge comprisesone asphere, while the second of the two bulges comprises 2 aspheres.

The aspheric surfaces of the example of tab. 3 are described by${P(h)} = {\frac{\delta*h^{2}}{1 +  \sqrt{}1  - {( {1 - {EX}} )*\delta^{2}*h^{2}}} + {C_{1}h^{4}} + \ldots + {C_{n}h^{{2n} + 2}}}$

Where P is the height deviation as a function of the radius h (rayheight with respect to the optical axis) with the aspheric constants C₁to C₆ as given in table 3.δis the inverse of the radius given in thetable.

The objective has a high correction quality, as the wavefront errorcalculated for two lines of 1 pm spectral distance is less than 8millilambda at the maximum field height and reduces to less than fivemillilambda on the optical axis.

The central obscuration of the system can be designed to need byenlarging distance and diameter of the mirrors 440, 441 of the catoptricpartial objective S42.

Ring sector field imaging is conventional with many catoptric andcatadioptric projection exposure systems of generally asymmetricconstruction. Such can also be realized within the invention. Then, themirrors only need an off-axis ring sector opening for entering of thelight beam, and consequently the pupil only has a two sector obscurationwith further reduced effects compared to the circular centralobscuration.

FIG. 5 schematically shows a microscope with an objective according tothe invention.

As such primarily makes sense for a DUV/VUV inspection microscope,direct visual observation by an ocular is not shown, but an imagedetector CCD of any appropriate known sort is provided in the imageplane of the objective. The objective is constituted by two refractivepartial objectives S51, S53 and the intermediate catoptric orcatadioptric partial objective S52. The example shows two coaxialopposite mirrors M1, M2 and one negative lens L in it.

The design of the objective is generally as shown in the embodimentsdescribed above, but with image and object plane exchanged to obtainmagnification, and with higher imaging ratio and smaller field.

An illumination system III illuminates the object Ob appropriately.

TABLE 1 0, 75 N.A., −2 = 157 nm, β = 6X, 17 × 7 min double-telecentricRADIUS THICKNESS APERTURE Element [mm] [mm] RADIUS [mm] OB — 41.365  1207.804 15.0000 64  2 7154.0 85.7060  3 −148.152 10.000 60  4 −480.52327.979  5 275.460 21.000 68  6 −420.424 18.169  7 91.68 20.000 62  8231.534 102.963  9 −62.100 5.000 25 10 551.104 10.065 11 −77.910 9.00032 12 −47.566 1.000 13 −281.444 12.500 41 14 −83.966 1.000 15 −1256.917.000 43 16 −69.116 1.000 17 99.668 7.000 40 18 60.790 0.978 19 63.02218.000 37 20 −177.094 1.000 21 65.632 5.000 22 43.522 9.388 23 44.5977.000 23 24 115.690 20.474 IMI1 — −5.072 M 2 220.905 16.140 115 25349.084 11.500 112 26 150.213 131.449 27 −163.770 11.500 105 28 −381.15817.158 M1 −228.356 115 29 −42.092 21.059 35 30 −51.728 1.000 31 −194.93718.000 59 32 −113.392 1.000 33 −1132.0 18.000 70 34 −193.134 1.000 35458.425 18.000 74 36 −386.456 93.349 37 171.069 27.160 78 38 −1302.61.000 39 115.683 12.796 71 40 79.902 53.335 41 −108.436 37.180 61 42−140.231 1.000 43 171.662 24.000 71 44 −1877.0 29.921 45 −118.760 37.45666 46 −131.389 1.000 47 153.982 21.000 73 48 1445.6 1.049 49 72.39620.001 59 50 76.113 1.000 51 53.654 49.996 49 52 69.967 16.341 LM — —Aspheric Surface Data 9: AS0 = 0 AS1 = 0 AS2 = −1.6880e−06 AS3 =1.5172e−10 AS4 = −1.1366e−12/AS5 = 1.3050e−16/AS6 = 1.7402e−18 AS7 =−2.4094e−21 M1: AS0 = 0 AS1 = 0 AS2 = −2.1332e−09 AS3 = −1.157e−13 AS4 =−2.4958e−18/AS5 2.735e−23/AS6 = −7.4436e−27 AS7 = 1.5059e−31 M2: AS0 = 0AS1 = 0 AS2 = 1.7841e−09 AS3 = 6.8616e−14 AS4 = 3.6976e−18/AS5 =5.2619e−23/AS6 = −2.331e−27 AS7 = 2.8845e−31 M1, M2 central hole r =15,3 nm Index of refraction CaF₂ at 157 nm: n = 1,55971

TABLE 2 5x, .75 N.A., 22 × 9 mm, λ = .157 μm RADIUS THICKNESS APERTUREElement [mm] [mm] RADIUS [mm] OB Telecentric 34.000 201 170.721 15.00073 202 183.404 70.512 203 −88.583 10.000 72 204 −109.418 0.097 205489.985 31.998 86 206 −223.861 105.847 207 211.214 18.000 80 208 1008.7132.111 209 98.261 7.000 38 210 75.231 9.337 OD — 6.429 obscuring disk r= 6,75 mm 211 −105.403 28.061 35 212 −103.952 1.000 213 2546.4 21.782 56214 −129.850 1.000 215 459.497 25.167 59 216 −117.119 1.000 217 76.2977.000 50 218 52.636 5.014 219 60.098 27.883 45 220 −254.989 1.000 221158.480 18.301 38 222 −1889.6 19.412 IMI −4.449 M2 198.917 11.198 115223 249.698 11.500 115 224 141.621 95.251 225 −146.113 11.500 105 226−279.951 14.507 M1 −195.876126 115 IMI — 27.988 227 −29.245 26.188 28228 −38.617 1.000 229 −212.943 16.904 64 230 −108.498 1.000 231 −1195.719.000 74 232 −186.309 1.000 233 397.280 24.000 82 234 −447.100 40.123235 184.325 28.000 82 236 −5827.0 1.000 237 94.479 15.000 71 238 73.23552.490 239 −84.776 10.000 58 240 −134.685 0.997 241 548.320 30.000 72242 −202.022 1.370 243 244.314 24.000 71 244 −390.876 9.997 245 −154.77926.099 69 246 −221.429 1.000 247 170.308 27.000 69 248 5689.0 1.000 24982.493 29.706 58 250 66.456 1.000 251 38.604 31.198 38 252 74.002 16.468IM — — 11.9 Aspheric Surface Data Surface 209 AS0 = 0 AS1 = 0 AS2 =−1.9059e−17 AS3 = 5.2904e−10/AS4 = −2.9602e−13/AS5 = 2.9727e−16 AS6 =−3.3981e−19/AS7 = 3.3404e−23 Surface 217 AS0 = 0 AS1 = 0 AS2 =−2.7436e−07 AS3 = −1.1707e−12/AS4 = −1.1841e−14/AS5 = 1.8131e−17 AS6 =−7.5053e−21/AS7 = 1.3749e−24 Surface M1 AS0 = 0 AS1 = 0 AS2 = 1.9405e−09AS3 = 9.5605e−14/AS4 = −2.6901e−17/AS5 = 5.9514e−23 AS6 =−7.7031e−26/AS7 = 1.8364e−30 Surface M2 AS0 = 0 AS1 = 0 AS2 = 3.2910e−09AS3 = 1.4964e−13/AS4 = −1.2351e−17/AS5 = 2.4844e−21 AS6 =−1.9615e−25/AS7 = 6.7644e−30 M1, M2 central hole r = 15,5 mm

TABLE 3 SURFACE RADII THICKNESS MATERIAL Ob 31.542 402 161.992 15.188LiF 403 469.503 19.672 404 231.249 8.649 LiF 405 323.702 81.163 406−125.044 7.000 LiF 407 1233.917 29.038 408 −136.3150 28.504 NaF 409−110.661 42.403 410 166.198 38.763 LiF 411 −426.980 33.045 412 102.98742.894 LiF 413 −497.639 3.533 414 −344.154 7.000 NaF 415 110.870 62.455416 −313.200 7.000 LiF 417 306.167 12.322 AS1 ∞ 4.589 419 −294.9867 7.21NaF 420 139.1333 10.42 421 −198.121 17.91 LiF 422 −67.419 .7642 423−423.496 14.9924 LiF 424 −117.918 .8112 425 743.808 8.0149 NaF 426123.869 .9171 427 128.249 44.3083 LiF 428 −90.153 .8501 429 230.30311.2449 LiF 430 1688.121 1.1630 431 122.245 7.9843 NaF 432 59.579 .7500433 60.793 24.9206 LiF 434 −934.252 1.1385 435 87.724 10.9289 LiF 43674.6528 7.4167 437 43.171 13.3010 LiF 438 47.425 5.000 IMI1 ∞ 135.0601440 −248.671 −135.0601 441 243.629 135.2019 IMI2 ∞ 21.4887 443 −39.7132927.9107 LiF 444 −53.040 2.7851 445 −218.179 26.3722 LiF 446 −100.4612.5410 447 −444.958 33.4544 LiF 448 −125.627 3.4864 449 205.875 52.0553LiF 450 −445.534 3.1476 451 −393.14835 7.1061 NaF 452 529.85954 10.9028453 171.69804 54.8263 LiF 454 −3285.94521 2.9859 455 1249.94523 10.7714NaF 456 188.56505 56.9985 457 −102.09026 18.5249 LiF 458 −114.021673.1811 459 −108.06602 36.3405 LiF 460 −122.25579 .8148 461 237.9389630.4791 462 −591.44374 33.927 463 −131.73596 9.2936 NaF 464 −816.0224.0340 465 −921.759 43.70 LiF 466 −161.952 12.96 467 135.682 35.56 LiF468 485.873 7.77 469 74.486 26.357 LiF 470 88.618 3.623 471 64.86156.517 LiF 472 65.449 20.524 Im ∞ Aspheric constants 11 A C1 .4365053E−07 C2 −.10565814E−11 C3  .33243511E−16 C4 −.27930883E−20 C5 .11432015E−24 C6 −.33257819E−29 19 A C1 −.96601938E−06 C2 .70267826E−10 C3  .31115875E−13 C4 −.43329420E−17 C5 −.41852201E−20 C6 .30053413E−25 25 A C1 −.29611487E−07 C2  .20760499E−10 C3−.12518124E−14 C4 −.52770520E−18 C5  .86996061E−22 C6 −.19792693E−27 34A C1 −.15885997E−06 C2  .52924012E−10 C3 −.73552870E−14 C4−.86379790E−18 C5  .59324551E−21 C6 −.39153227E−25 40 A C1 .23060301E−07 C2  .81122530E−13 C3 =.32179819E−17 C4  .71766836E−21 C5−.46055104E−26 C6  .12956188E−31 41 A C1 −.11072232E−07 C2 .31369498E−13 C3  .77375306E−17 C4  .19892497E−21 C5 −.89740115E−26 C6 .68627541E−31 49 A C1  .56699275E−08 C2  .57127904E−12 C3 .59227712E−16 C4  .21077816E−20 C5  .15595431E−24 C6 −.13690607E−29 63A C1 −.17174244E−07 C2  .18473484E−11 C3 −.42802250E−16 C4 .51394491E−20 C5 −.37650847E−24 C6  .22638360E−28 68 A C1 .10650246E−07 C2  .20265609E−11 C3 −.88014450E−16 C4  .91073382E−20 C5−.55181052E−24 C6  .37391374E−28

1. An objective comprising axial symmetry, at least one curved mirrorand at least one lens and two intermediate images.
 2. An objectiveaccording to claim 1 comprising two refractive partial objectives andone catadioptric partial objective.
 3. An objective according to claim 1comprising a first partial objective, a first intermediate image, asecond partial objective, a second intermediate image, a third partialobjective, wherein at least one of said partial objectives is purelyrefractive.
 4. An objective according to claim 1 comprising at least afirst partial objective, an intermediate image, a second partialobjective, one of said partial objectives being purely refractive andone being purely catoptric.
 5. An objective according to claim 1,flintier further comprising a partial objective with two opposingconcave mirrors with central bores, and with an optical axis, saidconcave mirrors being arranged axially symmetric with respect to saidoptical axis, their concave surfaces facing each other.
 6. An objectiveaccording to claim 5, wherein each of said concave mirrors has a vertexsituated on said optical axis, and wherein each of said intermediateimages has a maximum image height and is given on a surface with apiercing point on said optical axis, and at least one of said vertici isdistant from at least one of said piercing points by a distance lessthan the maximum image height of the image having said piercing point.7. An objective according to claim 5, wherein at least one lens isarranged in the beam path between the two concave mirrors.
 8. Anobjective according to claim 7, herein wherein said at least one lenshas negative refractive power.
 9. An objective according to claim 5,wherein said concave mirrors have central openings with a radius, eachof said radii being no greater than 1.5 times the maximum image heightof the neighboring intermediate image.
 10. An objective according toclaim 5, wherein each of the radii of said central openings is less than25% of the maximum light beam height at said concave mirror.
 11. Anobjective according to claim 5, wherein the light beam has a chief rayheight at each of the bores, which is of equal value but opposite signat the two bores.
 12. An objective according to claim 1, wherein a firstrefractive partial objective, a partial objective comprising at leastone mirror, and a second refractive partial objective are arranged insequence.
 13. An objective according to claim 1 12, wherein at least onelens of said refractive partial objectives has an aspheric surface. 14.An objective according to claim 1 12, wherein at least one of saidpartial objectives comprises a diffractive optical element.
 15. Anobjective according to claim 1 12, wherein said partial objectivecomprising at least one mirror has a magnification ratio in the rangebetween −1/0.7 and −1/1.3.
 16. An objective according to claim 12,wherein the first refractive partial objective has a magnification ratioof −1/3 to −1/8.
 17. An objective according to claim 12, wherein thesecond refractive partial objective has a magnification ratio of −1/0.8to −1/2.
 18. An objective according to claim 1 12, wherein at least oneof the first and second refractive partial objectives consists of afirst positive lens group, a negative lens group and a second positivelens group.
 19. An objective according to claim 1 18, wherein saidnegative lens group comprises at least two negative menisci, theirconcave surfaces facing each other.
 20. An objective according to claim18, wherein at least one of said first and second positive lens groupscomprises at least four positive lenses.
 21. An objective according toclaim 1, wherein all lenses contained are made of the same material,preferably a fluoride crystal.
 22. An objective according to claim 4,wherein lenses are made from at least two different fluorides.
 23. Anobjective according to claim 1, wherein the image field is an off-axisring sector.
 24. An objective according to claim 1 3, wherein the firstpartial objective has a pupil plane and a central obscuration device islocated near said pupil plane.
 25. An objective according to claim 1 3,wherein at least one of the refractive partial objectives has at least afirst lens group and a second lens group, one of them having lesser lensdiameters.
 26. An objective according to claim 14 25, wherein the atleast one aspherical lens surface is on a lens of the lens group withlesser lens diameters.
 27. An objective according to claim 1 3, whereinthe third partial objective has at least one positive concave air lensnear its pupil plane, namely located at a distance from the secondintermediate image of between 25% and 75% of the length of this partialobjective.
 28. An objective according to claim 1 3, wherein the imageside partial objective has two first lenses subsequent to the secondintermediate image, which are menisci concave on the side of theintermediate image, and two last lenses adjacent to the image, which aremeniscus concave on the side of the image.
 29. An objective according toclaim 1, wherein the image side partial objective arranged at an imageside has a pupil plane and at least one lens arranged at a distance fromthe image plane of between 25% and 75% of the length of the image sidesaid partial objective is a meniscus concave toward the pupil plane. 30.A microscope comprising an objective according to claim
 1. 31. Amicrolithographic projection exposure apparatus comprising a projectionobjective according to claim
 1. 32. Use of a projection an objectiveaccording to claim 1 for microlithographic projection exposure. 33.Method of microlithographic structuring of a substrate comprising thesteps of illuminating a mask with VUV light and projecting an image ofsaid mask onto said substrate through a projection an objectiveaccording to claim
 1. 34. An objective according to claim 6 5, whereinat least one lens is arranged in the beam path between the two concavemirrors.
 35. An objective according to claim 15, wherein the firstrefractive partial objective has a magnification ratio of −1/3 to −1/8.36. An objective according to claim 15, wherein the second refractivepartial objective has a magnification ratio of −1/0.8 to −1/2.
 37. Anobjective according to claim 16, wherein the second refractive partialobjective has a magnification ratio of −1/0.8 to −1/2.
 38. An objectiveaccording to claim 19, wherein at least one of said first and secondpositive lens groups comprises at least four positive lenses.
 39. Anobjective according to claim 25, wherein the at least one asphericallens surface is on a lens of the lens group with lesser lens diameters.40. A microlithography projection exposure apparatus comprising aprojection objective according to claim
 3. 41. Use of a projectionobjective according to claim 3 for microlithography projection exposure.42. Method of microlithographic structuring of a substrate comprisingthe steps of illuminating a mask with VUV light and projecting an imageof said mask onto said substrate through a projection objectiveaccording to claim
 3. 43. A microlithographic projection exposureapparatus comprising a projection objective according to claim
 4. 44.Use of a projection objective according to claim 4 for microlithographicprojection exposure.
 45. Method of microlithographic structuring of asubstrate comprising the steps of illuminating a mask with VUV light andprojecting an image of said mask onto said substrate through aprojection objective according to claim
 4. 46. A microscope comprisingan objective according to claim
 5. 47. A microlithographic projectionexposure apparatus comprising a projection objective according to claim5.
 48. Use of a projection objective according to claim 5 formicrolithographic projection exposure.
 49. A catadioptric objectivecomprising axial symmetry and at least a first partial objective, anintermediate image, and a second partial objective, one of said partialobjectives being purely refractive and one being purely catoptric.
 50. Amicroscope comprising an objective according to claim
 49. 51. Amicrolithographic projection exposure apparatus comprising a projectionobjective according to claim
 49. 52. Use of a projection objectiveaccording to claim 49 for microlithographic projection exposure.
 53. Anobjective comprising axial symmetry, an optical axis not being folded,at least one curved mirror and at least one lens and two intermediateimages, and providing an image reduction.
 54. An objective comprisingaxial symmetry, at least one curved mirror and at least one lens and twointermediate images, further comprising a partial objective with twoopposing concave mirrors with central bores, and with an optical axis,said concave mirrors being arranged axially symmetric with respect tosaid optical axis, their concave surfaces facing each other.
 55. Anobjective comprising axial symmetry, at least one curved mirror and atleast one lens and two intermediate images, further comprising a partialobjective with two opposing concave mirrors with central bores, and withan optical axis, said concave mirrors being arranged axially symmetricwith respect to said optical axis, their concave surfaces facing eachother, wherein a first refractive partial objective, a partial objectivecomprising at least one mirror, and a second refractive partialobjective are arranged in sequence, wherein the first refractive partialobjective has a magnification ratio of −1/3 to −1/8.
 56. An objectivecomprising axial symmetry, at least one curved mirror and at least onelens and two intermediate images, further comprising a partial objectivewith two opposing concave mirrors with central bores, and with anoptical axis, said concave mirrors being arranged axially symmetric withrespect to said optical axis, their concave surfaces facing each other,wherein a first refractive partial objective, a partial objectivecomprising at least one mirror, and a second refractive partialobjective are arranged in sequence, wherein at least one of the firstand second refractive partial objectives consists of a first positivelens group, a negative lens group and a second positive lens group. 57.An objective comprising axial symmetry, at least one curved mirror andat least one lens and two intermediate images, further comprising apartial objective with two opposing concave mirrors with central bores,and with an optical axis, said concave mirrors being arranged axiallysymmetric with respect to said optical axis, their concave surfacesfacing each other, wherein a first refractive partial objective, apartial objective comprising at least one mirror, and a secondrefractive partial objective are arranged in sequence, wherein saidnegative lens group comprises at least two negative menisci, theirconcave surfaces facing each other.
 58. An objective comprising axialsymmetry, at least one curved mirror and at least one lens and twointermediate images, wherein a first refractive partial objective, apartial objective comprising at least one mirror, and a secondrefractive partial objective are arranged in sequence, wherein at leastone aspherical lens surface is on a lens of a lens group with lesserlens diameters.
 59. An objective comprising axial symmetry, at least onecurved mirror and at least one lens and two intermediate images, a firstpartial objective, a first intermediate image, a second partialobjective, a second intermediate image, a third partial objective,wherein the third partial objective has at least one positive concaveair lens near its pupil plane, located at a distance from the secondintermediate image of between 25% and 75% of the length of this partialobjective.
 60. An objective comprising axial symmetry, at least onecurved mirror and at least one lens and two intermediate images, a firstpartial objective, a first intermediate image, a second partialobjective, a second intermediate image, a third partial objective,wherein an image side partial objective has two first lenses subsequentto the second intermediate image, which are menisci concave on the sideof the intermediate image, and two last lenses adjacent to the image,which are meniscus menisci concave on the side of the image.
 61. Anobjective comprising axial symmetry, at least one curved mirror and atleast one lens and two intermediate images, a first partial objective, afirst intermediate image, a second partial objective, a secondintermediate image, a third partial objective, wherein an image sidepartial objective has a pupil plane, and at least one lens arranged at adistance from the image plane of between 25% and 75% of the length ofthe image side partial objective is a meniscus concave toward the pupilplane.
 62. An objective comprising axial symmetry, at least one curvedmirror and at least one lens and two intermediate images, wherein atleast one lens is arranged in a beam path between the two concavemirrors.
 63. An objective comprising axial symmetry, at least one curvedmirror and at least one lens and two intermediate images, furthercomprising a partial objective with two opposing concave mirrors withcentral bores, and with an optical axis, said concave mirrors beingarranged axially symmetric with respect to said optical axis, theirconcave surfaces facing each other, wherein each of said concave mirrorshas a vertex situated on said optical axis, and wherein each of saidintermediate images has a maximum image height and is given on a surfacewith a piercing point on said optical axis, and at least one of saidvertici is spaced from at least one of said piercing points by adistance less than the maximum image height of the image having saidpiercing point.
 64. An objective comprising axial symmetry, at least onecurved mirror and at least one lens and two intermediate images, whereinthe first a refractive partial objective has a magnification ratio of−1/3 to −1/8.
 65. An objective according to claim 1, wherein the imagefield is off-axis.
 66. An objective according to claim 1, wherein saidat least one curved mirror has an off-axis opening.
 67. Amicrolithographic projection exposure objective comprising at least twoconcave mirrors with off axis openings, at least one intermediate image,and at least one purely refractive partial objective.
 68. An objectivecomprising a purely catoptric partial objective, a purely refractivepartial objective, an intermediate image between these partialobjectives, said purely catoptric objective comprising mirrors with anoff-axis opening.
 69. An objective being a microlithographic reductionprojection exposure objective comprising a catadioptric partialobjective with two opposite concave mirrors and a magnification ratio inthe range between −1/0.7 and −1/1.3; and a purely refractive partialobjective comprising at least one lens with an aspheric surface, theobjective being both side telecentric.
 70. The objective of claim 69,comprising a second intermediate image and another partial objective.71. The objective of claim 69, wherein said purely refractive partialobjective has a magnification ratio of −1/3 to −1/8.
 72. The objectiveof claim 69, wherein said catoptric partial objective comprises at leastone lens arranged in the beam path between the two concave mirrors. 73.The objective of claim 69, wherein the image field is off-axis.
 74. Theobjective of claim 69, wherein said two opposite concave mirrors haveoff-axis openings.